Drilling wells for various purposes is well-known. Such wells may be drilled for geothermal purposes, to produce hydrocarbons (e.g., oil and gas), to produce water, and so on. Well depth may range from a few thousand feet to 25,000 feet or more. In hydrocarbon wells, downhole tools often incorporate various sensors, instruments and control devices in order to carry out any number of downhole operations. Thus, the tools may include sensors and/or electronics for formation evaluation, fluid analysis, monitoring and controlling the tool itself, and so on. Tools that allow testing of fluid properties using instruments located downhole are known.